1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cstdlib>
 5 #include <algorithm>
 6 using namespace std;
 7 #define inf 999999
 8 #define N 2013
 9 int n,dis[N],vis[N],g[N][N];
10 char s[N][10];
11
12 int prim(int st)
13 {
14     for(int i=1; i<=n; i++)
15     {
16         dis[i] = g[i][st];
17         vis[i] = 0;
18     }
19     dis[st] = 0 ; vis[st] = 1;
20     int cost = 0;
21     for(int T=1; T<n; T++)
22     {
23         int mindis = inf ,idx = -1;
24         for(int i=1; i<=n; i++)
25         {
26             if(!vis[i] && dis[i] < mindis)
27             {
28                 mindis = dis[i];
29                 idx = i;
30             }
31         }
32         cost += mindis;
33         if(idx==-1) return -1;
34         vis[idx] = 1;
35         for(int i=1; i<=n; i++)
36         {
37             if(!vis[i] && dis[i] > g[i][idx])
38             dis[i] = g[i][idx];
39         }
40     }
41     return cost;
42 }
43
44 int main()
45 {
46     while(scanf("%d",&n)&&n)
47     {
48         for(int i=1; i<=n; i++)
49         for(int j=1; j<=n; j++)
50         {
51             if(i==j) g[i][j] = 0;
52             else g[i][j] = inf;
53         }
54         for(int i=1; i<=n; i++)
55         cin>>s[i];
56         for(int i=1; i<=n; i++)
57         {
58             for(int j=i+1; j<=n; j++)
59             {
60                 int cnt = 0;
61                 for(int k=0; k<7; k++)
62                 {
63                     if(s[i][k]!=s[j][k])
64                     cnt++;
65                 }
66                 g[i][j] = g[j][i] = cnt;
67             }
68         }
69         printf("The highest possible quality is 1/%d.\n",prim(1));
70     }
71     return 0;
72 }